The transmission of shock forces from a hammer to the hand and forearm of the user is a common problem. For example, when a hammer is struck against an unyielding object with significant force, the shock to the user's hand can be quite severe. The problem is especially acute for persons who make regular use of hammers as part of their occupation, such as, for example mechanics who use large mallets or other hammers to break nuts/bolts or other fittings loose on heavy equipment.
A related problem occurs when the head of the hammer/mallet misses the object, and the impact is received at the shank of the handle. Not only does this result in a particularly severe shock to the user's hand, but the shank can fracture or break, in which case the separation of the head from the handle can present a serious safety hazard.
There have been attempts to provide a hammer having a handle which reduces the transmission of shocks to the user, but these have not been very satisfactory in practice. For example, fiberglass handles, although superior to traditional wood and steel in some respects, still transmit most of the shock directly to the hand grip. Moreover, although durable within limits, such handles are subject to the fractures/breakage problem discussed above. Still further, the use of separate materials--e.g., metal, fiberglass, rubber--for the head and other components means added costs in assembly.
Some success has also been achieved using hammers or mallets cast of urethane or similar materials. Such units, being formed of a non-metallic material, are especially valuable in electrical work because they are non-conductive, and also in flammable environments and explosive atmospheres due to their non-sparking nature. It has not been possible, however, to achieve a satisfactory balance between the competing requirements of the head and handle portions of the hammer when using this material. For example, if the material is sufficiently resilient for the shank of the handle to effectively absorb the impact loads, then the head of the hammer or mallet will be too soft to provide a satisfactory striking face or to have adequate service life; also, an excessively flexible handle tends to result in unacceptable, "floppy" handling characteristics. On the other hand, if the material has sufficiently high durometer to form a satisfactory head, the handle is too rigid to absorb the shock, and will also be subject to breaking.
Another difficulty with prior art cast urethane hammers/mallets has been to provide the head portion of the tool with sufficient weight/mass. Because of the low density which is characteristic of urethane and similar materials, it is necessary to augment the head with a denser metal core or weight if the hammer is to generate sufficient driving force. The metal weight must be located centrally in the head portion in order to provide the hammer/mallet with proper handling characteristics, but this has been difficult to achieve economically, due to the need for special struts or other supports to hold the metal core in the correct position within the mold while the unit is being cast.
Accordingly, there has existed a need for a hammer or mallet formed of a non-metallic material such as cast urethane, in which the head has sufficient hardness (or durometer) to provide a satisfactory striking surface, yet in which the handle portion has sufficient flexibility and resiliency to absorb and reduce the impact loads without transmitting these directly to the hand or arm of the user. Furthermore, there is a need for such a hammer or mallet in which the impact-absorbing handle provides sufficient stability to the head portion to ensure good handling characteristics during use. Still further, there is a need for such a hammer or mallet which can be constructed economically without the need for assembling several components made of different materials. Still further, there is a need for such a a hammer/mallet which can be cast of non-metallic material, with a central metallic core for adding weight to the head portion, but without requiring special struts or other supports for positioning the core within the mold during casting.